The biggest improvement would the be the addition of Audyssey. The 3312CI uses MultEQ XT while the 4311CI uses the even more advanced MultEQ XT32, although costs about 2x that of the 3312CI. If you never expect to expand beyond 7.1, or want the ability to individually calibrate 2 subs, the 3312CI should serve you well. Both these units can be had at a discount by several of the on-line authorized resellers including AV Science and Electronics Expo, but you must "call" them as they list MSRP on their websites.